Overview
The numerical control device is the core of the machine tool's numerical control system and understands its main role in the system, due to its importance in the entire system.
First, the composition of the CNC device
From the point of view of automatic control, the CNC system is a position (track) control system, which is essentially an automatic control system in which the displacements of multiple execution components (moving axes) are controlled and coordinated motion is performed. A computer control system with a dedicated operating system.
From an external point of view, the CNC system is composed of hardware (general hardware and dedicated hardware) and software (dedicated).
Figure 5-1 Hierarchy of the CNC system hardware
1, the hierarchical structure of the CNC system hardware
It consists of three parts: computer basic system, equipment support layer and equipment layer.
2. Functional structure of CNC system softwareIn terms of essential characteristics, CNC system software is a dedicated operating system with real-time and multi-tasking capabilities. From the perspective of functional features, the dedicated operating system consists of two parts: CNC management software and CNC control software. It is the living soul of the CNC system.
Its block diagram is shown in Figure 5-2.
3, CNC hardware and software functions and mutual relations
Hardware is the foundation, software is the soul
The system software of the CNC device, with the support of the system hardware, organizes and manages the work of the entire system in a reasonable manner and realizes various numerical control functions. The CNC machine tool can be processed in an orderly manner according to the operator's requirements.
The hardware and software of the CNC system form the system platform of the CNC system, as shown in Figure 5-3.
The platform has the following two implications:
Provide the basic functions of the basic configuration of the CNC system;
On the platform, function design and development can be performed according to the user's requirements.
Second, the advantages of CNC devices
1, with flexibility and versatility
The functions of the CNC device are mostly implemented by software, and the software and hardware adopt a modular structure, which makes the modification and expansion of system functions more flexible.
The basic configuration part of the CNC device is universal, and different CNC machine tools only configure corresponding specific function modules to achieve specific control functions.
2, rich numerical control function
Interpolation function: quadratic curve, spline curve, space surface interpolation;
Compensation function: motion accuracy compensation, random error compensation, nonlinear error compensation, etc.
Man-machine conversation function: dynamic and static tracking display of processing, advanced man-machine dialogue window
Programming functions: G code, basket programming, partially automatic programming.
3, high reliability
The use of highly integrated electronic components, chips, and VLSI (very large scale integrated circuits) is a guarantee of reliability for CNC devices.
Many functions are implemented by software, reducing the amount of hardware.
Abundant fault diagnosis and protection functions (mostly implemented by software) can reduce the frequency of system failures and repair time after failures.
4, easy to use and maintain
Easy to use and operate: The user can perform correct operation only according to the menu prompts.
Easy to program: With a variety of programming features, automatic program verification and simulation capabilities.
Easy Maintenance and Maintenance: Some routine maintenance work is performed automatically (lubrication, regular inspection of key components, etc.), and the self-diagnostic function of CNC machine tools can quickly locate faults accurately.
5, easy to implement mechatronics
The small size of the control cabinet of the CNC system (the reduction in the number of computers and hardware, the increasing integration of electronic components, and the continuous reduction of hardware) make it possible to integrate them physically with the machine tool and reduce the floor space. Easy to operate.
Third, the function of the CNC device
The function of the CNC device refers to the method and means to satisfy the user's operation and machine control requirements. The functions of the numerical control device include basic functions and selection functions.
Basic functions - functions of the basic configuration of the numerical control system, ie essential functions;
Selection function - The function that the user can select according to actual requirements.
1, control function
—— Number of axes that can be controlled and controlled by the CNC
CNC Axes Category:
Move axes (X, Y, Z) and rotary axes (A, B, C);
Basic and additional axes (U, V, W).
The greater the number of linked control axes, the more complex the CNC system and the more difficult it is to program.
2, ready function (G function)
—— The function of commanding the machine action mode.
3, interpolation function and fixed cycle function
—— The interpolation function is the function of the CNC system to realize the processing of the part profile (plane or space).
—— The canned cycle function is a typical machining cycle in the CNC system. (such as drilling, tapping, boring, deep hole drilling and thread cutting, etc.)
4〠Feed function
——Feed speed control function.
Feedrate - Controls the speed of the tool relative to the workpiece in mm/min.
Synchronous feedrate - Synchronization of cutting speed and feedrate in mm/r.
Feedrate override (feedrate override) - Manual override of a given feedrate in real-time.
5, spindle function
—— The control function of the spindle of the CNC system.
Spindle speed - The spindle speed control function in r/min.
Constant speed control - The cutting speed of the tool cutting point is a constant speed control function.
Spindle orientation control - The function of the main axis is positioned at a specific position.
C-axis control - The function of the spindle circumference arbitrary position control.
Spindle Adjustment Rate - Manually adjust the preset spindle speed in real time.
6, auxiliary functions (M function)
—— The function for instructing the auxiliary operations of the machine.
7ã€Tool management function
- Realize management functions for tool geometry and life.
Tool geometry (radius and length) for tool compensation functions;
The tool life refers to the time life, when the tool life expires, the CNC system will prompt the user to change the tool;
The CNC system has a tool number (T) management function that identifies the tool in the magazine and automatically selects the machining tool.
8, compensation function
Tool radius and length compensation function: The function of controlling the tool center trajectory by programming programmed by the part contour.
Drive chain error: including pitch error compensation and backlash error compensation.
Non-linear error compensation function: Models such as thermal deformation, static elastic deformation, spatial errors, and machining errors caused by tool wear are modeled using new technologies such as AI and expert systems, and online compensation is performed using the model.
9. Man-machine conversation function
In the CNC device such functions include:
Menu structure operation interface;
Part editing program editing environment;
System and machine parameters, status, fault information display, query or modify the screen.
10, self-diagnosis function
—— CNC automatically implements fault prediction and fault location.
Boot self-diagnosis;
Online self-diagnosis;
Offline self-diagnosis;
Telecommunication diagnostics.
11ã€Communication function
- CNC's ability to exchange information and data with the outside world
RS 232C interface, can transmit parts processing program;
DNC interface, can realize direct numerical control;
MAP (Manufacturing Automation Protocol) module;
Network card: Adapt to the requirements of integration of manufacturing systems such as FMS, CIMS, and IMS.